FIELD OF THE INVENTION
The invention relates to a process diagnosis system and a method for the diagnosis of processes and states in a technical process. The method is, in particular, suitable for the diagnosis of processes and states of a power station plant.
In technical plants, it is generally known to carry out process diagnosis on the basis of acquired measurement signals. In known technical plants the actual measurement and data acquisition is realized decentrally. The subsequent diagnosis is carried out centrally in a process computer.
Furthermore, a plurality of procedures for carrying out technical diagnoses and process management are known. Novel types of approaches for advanced diagnosis are aimed at the integration of knowledge-based systems into process control technology. Such a system emerges from M. Polke, Proze.beta.leittechnik, Kapitel 'Integration Wissensbasierter Systeme in die Leittechnik, [Process Control Technology, Chapter on "Integration of Knowledge-Based Systems into Process Control Technology"], pp. 813 ff., Oldenbourg Verlag, 1994. In general, a diagnosis is carried out in several steps: fault detection, fault localization and fault cause determination. So-called alarm re ports, which are combined into alarm hierarchies, are widespread. Higher-quality forms of diagnosis are currently carried out in central, complex application programs, for example by expert systems.
The disadvantage of simple diagnostic methods based on alarm hierarchies is the inadequate fault detection and fault cause determination. In particular for a diagnosis in the case of transient processes, it is not sufficient to work using static error limits. In order to eliminate this problem, process-state dependent reference models were introduced. The reference models prescribe the expected set point and a maximum permissible deviation from the set point as a function of the current process state. If a deviation is detected, a downstream fault localization system calculates the fault location and the fault cause. Typically, this form of expanded process diagnosis is carried out by model-based or rule-based expert systems, such as those published, for example, in "Das Expertensystem MODI" ["The MODI Expert System"] in ABB Technik/6, 1994 (pages 38 to 46).
The disadvantages of the dynamic diagnostic method are, first, on account of the diagnosis being carried out centrally and because not all the process variables are available centrally, the diagnostic capability for specific plant components are limited. Second, the high engineering outlay to build up the reference models. Third, the high outlay in order to adapt the fault trees or rules for the fault causes to the respective plant. A further disadvantage of previous diagnostic applications is their inflexibility. More precisely, after changes are made to the plant, the diagnostic system has to be readjusted to account for the changes. In previous diagnostic applications, automatic adjustments are not possible.